Filter element, oil separator, and method for controlling prevailing pressure in crankcase ventilation system

ABSTRACT

The invention describes a filter element for an oil separator of a crankcase ventilation system in which a filter element is configured to separate oil from fluid and that has a covering surface extending parallel to a direction of flow, together with at least one cover element covering surface in at least some regions. An oil separator is taught having the filter element with at least one pressure control valve controlling crankcase pressure and has a valve closing body that operates in conjunction with a valve seat.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of application Ser. No. 15/169,848,filed Jun. 1, 2016, which claims a priority date of Jun. 1, 2015, basedon prior filed German patent application No. 10 2015 006 768.0, theentire contents of the aforesaid US application and the aforesaid Germanpatent application being incorporated herein by reference.

TECHNICAL FIELD

The invention relates to a filter element for an oil separator, an oilseparator of a crankcase ventilation system, and a method forcontrolling the prevailing pressure in a crankcase ventilation system.

BACKGROUND

With reciprocating piston internal combustion engines, an oil-containingleakage gas, so-called blow-by gas, is produced in the crankcase. Thereturn thereof into the combustion process is legally mandatedworldwide, and takes place in so-called closed crankcase ventilationsystems. The most important tasks of a crankcase ventilation system areoil separation and oil return into the crankcase, as well as theregulation of the crankcase pressure. The requirements for oilseparation have been steadily increasing in recent years, as legislationon emissions has grown increasingly stringent, in order to protectemissions-related engine components such as exhaust gas turbochargers,intercoolers, or sensors from performance loss due to oil contamination.Thus, oil separation is important not only in minimizing oilconsumption, but also in making what is now an essential contribution tocompliance with emissions legislation throughout the lifetime of thevehicle. In addition to oil separation, a crankcase ventilation systemcontains other important components, such as, for example, a pressurecontrol valve, depending on the ventilation design.

A pressure control valve for a crankcase ventilation system of aninternal combustion engine is disclosed, for example, in documents DE 102013 005 624 A1, WO 2005 088 417 A1 and WO 2007 13 50 82 A2.Generally-known pressure control valves have a valve closing body thatoperates in conjunction with a valve seat, and a return spring that actson the valve closing body in the direction facing away from the valveseat (DE 10 2004 02 22 75 A1).

In order to extend the life of the return spring in a pressure controlvalve for an internal combustion engine, DE 10 2004 02 22 75 A1 proposesarranging the return spring on the side of the valve closing body facingaway from the valve seat, and thus preventing the return spring fromcontacting aggressive blow-by gases emerging from the crankcase.Documents WO 2007 13 50 82 A2 and JP 2003 33 65 16 A disclose arrangingthe return spring on the atmosphere side of a pressure control valve.

WO 2005 08 84 17 A1, WO 2009 15 63 03 A1, DE 10 2004 02 22 75 A1, and EP1 32 95 98 A1 disclose fastening a membrane configured as a sealingelement onto a valve element by means of at least one spraying process,in particular, by injection-molding onto a valve element or overmoldinga valve element.

With known pressure control valves, the valve seat of the pressurecontrol valve is arranged on the outside of a side wall of the crankcaseventilation system (DE 10 2013 005 624 A1) or formed by a side wall ofthe housing of the crankcase ventilation system (WO 2005/088 417 A1).

The invention addresses the problem of developing a filter element ofthe afore-mentioned type, an oil separator of the aforementioned type,and a method of the aforementioned type, in such a manner that thefunctions thereof are optimized, in particular, that the crankcaseventilation system takes up the least installation space possible.

SUMMARY

The invention addresses the problem of developing a filter element ofthe afore-mentioned type, an oil separator of the aforementioned type,and a method of the aforementioned type, in such a manner that thefunctions thereof are optimized, in particular, that the crankcaseventilation system takes up the least installation space possible.

The invention is based on realizing the functions of the crankcaseventilation system with the fewest possible components.

According to the invention, the cover element of the filter elementcomprises at least one clean fluid discharge element that: leads outfrom the interior of the filter element; in particular, extends awayfrom the filter element; in particular, is tube-shaped; and isconfigured in order to remove the purified fluid, in particular, cleanair. The end surface of this clean fluid discharge element that facesaway from the filter element is configured as a sealing surface for avalve of the crankcase ventilation system, or comprises a sealingsurface for a valve of the crankcase ventilation system. Preferably, thesealing surface is a valve seat for a valve closing body, in particular,for a valve closing body sealing element of a pressure control valvethat surrounds the valve closing body. In addition to the function ofdischarging or removing the purified fluid, the clean fluid dischargeelement thus assumes another function, namely, a sealing function.

The sealing surface is substantially flat and free of burrs, wherein theends, margins, or edges of the sealing surface may be rounded. Inaddition, the sealing surface is preferably round, in particular,circular.

The arrangement of the sealing surface on the clean fluid dischargeelement, as described, causes the sealing surface and the plane definedthereby to be preferably spaced apart from the axial, outer surface ofthe cover element. This arrangement likewise defines the distance of thevalve from the cover element. Within this distance, the clean fluidoutlet of the oil separator housing, in which the filter element is tobe incorporated, can be advantageously arranged so as to conserveinstallation space. For a streamlined overall design, it is thereforepreferred that the length of the clean fluid discharge element, asmeasured from the axial, outer surface of the cover element, correspondsapproximately to the diameter of the clean fluid outlet of the oilseparator housing.

The cover element is preferably an end plate of the filter element. Thecover element is sealingly and non-releasably connected to the filtermedium at an end face of the filter element, for example, by gluing orwelding. The cover element is preferably produced from thermoplasticpolymer, preferably by injection molding.

The clean fluid discharge element is preferably non-releasably (i.e., soas not to be non-destructively removable) and sealingly connected to thecover element, so that the pre-filtration side is separated from thepost-filtration side. The clean fluid discharge element is particularlypreferably integral with the cover element.

The clean fluid discharge element and the cover element are preferablycontinuously closed. This means that the clean fluid discharge elementand the cover element are connected and designed such that other thanthe clean fluid exit opening surrounded by the sealing surface, no otheropenings are present in the cover element or clean fluid dischargeelement.

The clean fluid discharge element is preferably an oval cylindrical, inparticular, circular cylindrical, in particular, straight tube. Thistube comprises a closed cylindrical wall and two open ends, wherein thesealing surface is configured on one end that faces away from the coverelement, and the other end is connected to the cover element, so that afluid connection to the interior of the filter medium or filter body isformed. The ends are preferably oriented so as to be perpendicular tothe central axis.

In a particularly preferred embodiment, the cover element is an annularend plate away from which the clean fluid discharge element, configuredas a tube, extends on the side facing away from the filter medium.

The clean fluid element and the cover element preferably form anL-shaped or T-shaped cross-section.

A preferred embodiment of the filter element of the present inventioncomprises a clean fluid discharge element having an end surfaceconfigured so as to be flat and/or free of burrs in so as to be usableas a sealing surface, in particular, as a valve seat for a valve closingbody of a pressure control valve of the crankcase ventilation system.

A person skilled in the art will appreciate the filter element of thepresent invention, in particular, in use in a crankcase ventilationsystem having an integrated pressure control or integrated pressurecontrol valve. Namely, by means of the sealing surface according to theinvention, the filter element may assume another function beyondseparating oil from aerosol—namely, a partial function of the pressurecontrol. The sealing surface of the filter element may then serve as avalve seat for the valve closing body of the pressure control valve. Thesealing surface may also be configured in order to operate inconjunction with the control of the crankcase pressure, in particular,the limitation of the vacuum of the crankcase ventilation system.

The sealing surface of the filter element of the present invention makesit possible to significantly reduce the installation space for thecrankcase ventilation system in comparison to, for example, prior artdisclosed in documents DE 10 2013 005 624 A1 and WO 2005 088 417 A1, inwhich the valve seat of the pressure control valve is arranged on ahousing side wall of the crankcase ventilation system. Thus, due to thesealing surface of the filter element according to the invention, thecomponents of the pressure control valve, which is configured in orderto control the crankcase pressure, can be accommodated in the upperhousing part of the crankcase ventilation system.

A further reduction of the installation space can be achieved bydesigning the filter element so that the flow therethrough goes from theoutside to the inside and so as to have a cavity configured in order toremove the purified fluid, in the interior of the filter medium. Thus,as opposed the prior art, in which the flow through is from the insideto the outside, it is not necessary to provide a channel by means ofwhich the fluid can be delivered to the interior of the filter medium.

The cavity arranged in the interior of the filter medium and configuredin order to remove the fluid is advantageously connected directly to theclean fluid discharge element or transitions directly into a cavity ofthe clean fluid discharge element that is configured in order to removethe fluid.

In order to form the filter medium so as to be as stable as possibleagainst forces acting on the filter medium from the outside, the filtermedium advantageously has an oval, in particular, circularcross-section. In an advantageous embodiment of the crankcaseventilation system, the housing of the crankcase ventilation system thatis formed of at least one housing part and configured in order toaccommodate the filter medium also has an oval, in particular, circularcross-section.

As the filter medium, it is possible to use basically any material, inparticular, a non-woven fabric, for example, made of metal fiber, glassfiber, and/or plastic fiber, for example, made of polyester. It wouldalso be possible to combine these materials. In addition, as describedin DE 10 2011 016 893 A1, the filter medium may be a coalescence medium.Preferably, the filter element is an annular coalescence element. Forthis purpose, the filter element preferably has a filter mediumconfigured as a non-woven fabric that preferably is wrapped repeatedlyand thus in a plurality of layers annularly around a support tube. Thismeans that the filter medium is preferably configured as at least onenon-woven wrap. To stabilize and seal off, a cover element that ispreferably configured as an end plate is also provided on respective endfaces.

The oil separator is preferably configured, as described, as acoalescing filter. The crankcase ventilation system may be configured asa closed crankcase ventilation system in which the post-filtrationleakage gas is returned to the combustion process, or as an opencrankcase ventilation system.

The sealing surface of the filter element is particularly stable and isparticularly easy to produce if the sealing surface, the clean fluiddischarge element, and the cover element are integral with one another.

Independently thereof or in connection thereto, in a preferredembodiment of the filter element of the present invention, the sealingsurface and/or the end plate is made of a mechanically fixed and/orrigid material, for example, polyamide 66 having 35% glass fibers (PA 66GF35).

In order to improve the tightness of the sealing of the pressure controlvalve, the valve closing body has at least one elastic valve closingbody sealing element, at least on the region thereof that can bearranged in contact with the valve seat of the filter element.

The sealing element of the valve closing body advantageously hassubstantially at least one elastomer. In particular, the valve closingbody sealing element may be formed of at least one elastomer, forexample, ethylene acrylate rubber (EAR) and/or from, in particular,hydrogenated nitrile rubber ([H]NBR) and/or acrylate rubber. Incomparison to the prior art, in which the sealing off of the valve seatand the valve closing body is performed solely by hard components, thetightness of the seal of the pressure control valve may be considerablyimproved by the elastic configuration of the valve closing body sealingelement.

In an advantageous embodiment of an oil separator of the presentinvention, the sealing happens from soft to hard. Thus, for example, thevalve closing body and the clean fluid discharge element, in particular,the valve seat are formed essentially out of polyamide 66 with 35% glassfiber (PA 66 GF35) and the valve closing body sealing element is formedessentially out of ethylene acrylate rubber (EAR) and/or acrylaterubber.

The tightness of the seal of the pressure control valve can also beimproved by connecting the sealing element of the valve closing bodyfixedly or non-releasably to the valve closing body, in particular,application to the valve closing body by means of at least one sprayprocess. The valve closing body sealing element and the valve closingbody thus advantageously form a unit. In one advantageous embodiment ofthe present invention, the valve closing body sealing element is nottied up into the valve body, as is known in the prior art, but ratherthe valve body is encapsulated by the valve closing body sealingelement, and forms a solid unit with the valve closing body sealingelement.

Another limiting criterion of an advantageous embodiment of an oilseparator of the present invention relative to the prior art is thusthat the valve closing body and the valve closing body sealing elementare fixedly connected to one another. The valve closing body sealingelement thus forms a solid unit with the valve closing body, whichimproves the tightness of the seal.

A particularly high tightness of the seal of the pressure control valvemay also be achieved by configuring the valve closing body so as to beflat or level at a region thereof that faces the valve seat, inparticular, a region thereof that can be arranged in contact with thevalve seat of the filter element. In contrast, in the prior art, thevalve closing body is usually curved in the shape of a dish on theregion thereof that faces the valve seat. In contrast to the dish shapein the prior art, the valve closing body—in particular, the valveclosing body sealing element—of an optimized embodiment of an oilseparator of the present invention thus has a flat or level shape,whereby the sealing properties are greatly improved.

Independently thereof or in connection therewith, a particularlyadvantageous embodiment of an oil separator of the present invention hasan advantage over the prior art, for example, that is illustrated inFIG. 12, in that the components of the pressure control valve or thepressure control are located in the upper part of the housing.

A special feature of the present invention is that the unit filterelement constitutes the end position for the valve closing body.

Another special feature of the present invention is that the filterelement assumes two functions:

1. Separating oil from the gas

2. Partial function of the pressure control

BRIEF DESCRIPTION OF THE DRAWINGS

As already discussed above, there are several approaches toadvantageously embodying and developing the teaching of the presentinvention.

FIG. 1 illustrates a perspective view of an embodiment of a crankcaseventilation system according to the present invention, in which apressure control valve thereof works according to the method of thepresent invention;

FIG. 2 illustrates a longitudinal depiction of a crankcase ventilationsystem from FIG. 1, with an embodiment of an oil separator according tothe present invention, in which a pressure control valve thereof worksaccording to the method of the present invention;

FIG. 3 illustrates a longitudinal view of a detail of the oil separatorfrom FIG. 2;

FIG. 4 illustrates a plan view of the oil separator from FIG. 2;

FIG. 5 illustrates a perspective view of the valve closing body and thevalve closing body sealing element of the pressure control valve of theoil separator from FIG. 2;

FIG. 6 illustrates a longitudinal view of the valve closing body and thevalve closing body sealing element from FIG. 2;

FIG. 7 illustrates a perspective view of the valve closing body, areturn spring, and a pressure control insert of the oil separator fromFIG. 2;

FIG. 8 illustrates a perspective exploded view of the components of anembodiment of a filter element according to the present invention;

FIG. 9 illustrates a perspective exploded view of the componentsarranged in the housing cover of the crankcase ventilation systemdepicted in FIG. 1;

FIG. 10 illustrates a detail of the pressure control valve of thecrankcase ventilation system from FIG. 1, wherein the forces acting onthe valve closing body are marked;

FIG. 11 illustrates an embodiment of a control characteristic of thecrankcase pressure as a function of the vacuum on the outlet side of thepressure control valve of the crankcase ventilation system from FIG. 1;

FIG. 12 illustrates an oil separator according to the prior art; and

FIG. 13 illustrates a side view of the oil separator from FIG. 12, whichis configured according to the prior art.

Identical or similar designs, elements, or features are provided withidentical reference signs in FIG. 1 to 12.

DETAILED DESCRIPTION

FIG. 1 illustrates a perspective view of a crankcase 410 (shown onlyschematically), which comprises an oil separator 200 of a crankcaseventilation system. The crankcase 410 is part of an internal combustionengine. The internal combustion engine may be installed in a motorvehicle. The oil separator 200 is configured as an oil separator foroil-containing air from an interior of the crankcase 410. In suchapplications, the oil-containing air is usually mixed with combustiongases exiting from the cylinders as leakage gas into the crankcase. Thismixture is frequently also called crankcase gas, the term “air” stillalso being used for the sake of simplicity.

The oil separator 200 comprises a substantially oval-cylindrical—inparticular, circular-cylindrical—filter housing composed of a firstfilter housing part 210—namely, a housing cover—and a second filterhousing part 220—namely, a housing body. The second filter housing part220 has an inlet 222 for the oil-containing air 500. Arranged in thefilter housing is a filter element 100 comprising at least one filtermedium 10 made of a filter material that has been arranged in an annularshape, e.g., a circular ring shape or an oval ring shape (see FIG. 2).The filter element 100 is covered by the filter housing in FIG. 1, andtherefore is marked with a dashed reference line. Within the filterhousing 210, 220, the air 500 (a corresponding air flow 20 is indicatedin FIG. 2 by an arrow) is filtered by means of the filter medium 10. Theresulting clean air 510 is guided out of an interior 12 (FIG. 2)enclosed by the filter medium 10, through a clean air discharge element50 of the filter element 100, to a clean air outlet 212 of the housingcover 210, and from the clean air outlet 212 back into the intake ductof the internal combustion engine. Separated oil is removed through anoil outlet 230.

The oil separator 200 has a pressure control valve, in order to limitthe crankcase vacuum to a defined value. The pressure controlvalve—depicted by way of example in FIGS. 2 and 3—has a valve closingbody 310 that is surrounded by a valve closing body sealing element 320,preferably by a membrane, as is illustrated here.

On the end facing away from the valve closing body 310, the membrane 320is connected to the first filter housing part 210, for example, by beingclipped into the first filter housing part 210. Alternatively, themembrane 320 may also be mounted between the filter housing part 210 andthe cover element 214. Preferably, the membrane is clamped between thefirst filter housing part 210 and an insert 350 forming even morepreferably the lower stop of the spring 330, as in thepresently-described embodiment. The insert 350 has openings, so that theambient pressure can act on the membrane 320 and on the valve closingbody 310.

In order to be closed, the pressure control valve has a valve seat 52arranged on the filter element 100. In contrast to the prior artillustrated in FIGS. 12 and 13, the filter element 100 illustrated inFIGS. 2, 3, 8, and 10 has a cover element 40 that is configured as anend plate and has a sealing surface 52 at the end thereof that facesaway from the filter element 100, wherein this sealing surface 52 isprovided in order to seal off the pressure control valve 52, 310, 320,330, by the ability of the valve closing body sealing element 320 or thevalve closing body 310 to come into sealing contact with the sealingsurface 52, preferably with a contact surface 312 (see FIG. 6) of thevalve closing body 310 or the membrane 320.

The membrane 320 is configured to seal the clean air outlet 212 and theinterior 12 of the filter medium 10 off from the ambient air pressure,and to keep the valve closing body axially movable.

The valve closing body 310 can be moved relative to the valve seat 52,as illustrated in FIG. 10. The left side of the illustrated sectionalview depicts the closed state of the valve, where the valve closing body310 abuts, preferably axially (as is shown), against the sealing surface52 with a circular ring-shaped contact surface 312 (see FIG. 6); on theright side of the view, the valve closing body 310 is spaced apart fromthe sealing surface 52, so that the valve is open. The pressure controlvalve 52, 310, 320, 330 is configured so as to control the flow rate orvolume flow of the fluid flowing away through the clean fluid dischargeelement 50, by means of the movement of the valve closing body 310relative to the valve seat 52, in particular, through the modificationof the cross-section of the flow channel 340 formed by the gap betweenthe sealing surface 52 and the valve closing body 310.

The pressure control valve is configured such that the membrane 320 issubjected to the pressure 600 prevailing in the clean air outlet 212 onthe side thereof facing the filter element 100 or the housing interior,in the region of the circular ring area A_(M) defined by the diametersØ_(M) and Ø_(M), and the valve closing body 310 is subjected to thepressure 610 prevailing in the interior 12 of the filter medium 10 onthe side thereof facing the filter element 100 or the housing interior,in the region of the circular area A_(D) defined by the inner diameterØ₀ of the sealing surface 52. On the side facing away from the filterelement 100 or the housing interior, the membrane 320 and the valveclosing body 310 are also subjected to the ambient pressure. Preferablyalso provided is a return spring 330 that subjects the membrane 320and/or the valve closing body 310 to a force that acts in a direction ofopening, i.e., is directed away from the filter element 100. At leastone opening in a pressure control valve cover element 214 and/or aninsert 350 causes ambient pressure to be applied to the back side of themembrane; this ventilation makes it possible for the pressure controlvalve to work undamped.

Preferably, a return spring 330—as already described—is arranged on theside of the valve closing body 310 that faces away from the filterelement 100. The return spring 330 subjects the valve closing body 310and/or the membrane 320 arranged thereon to a force 620 (see FIG. 10)oriented away from the valve seat 52. The compression spring or returnspring 330 services to ensure the rest position of the valve closingbody 310. The rest position corresponds to the position of the valveclosing body 310 at which the force of the return spring 330 is exactlyas great as the sum of the force of the crankcase pressure 610 and theforce of the suction pressure 600.

On the way from the interior 12 of the filter medium 10 to the clean airoutlet 212, the clean fluid flows through a flow channel 340 (see FIGS.3 and 10) that is arranged between the valve closing body 310—inparticular, the membrane 320 arranged on the valve closing body 310—andthe valve seat 52, and that preferably has the shape of an annular gap,as is provided presently. The diameter of this flow channel 340 can bechanged or regulated through relative movement of the valve closing body310 to the valve seat 52.

With decreasing pressure in the clean air outlet 212 or on the exit sideof the pressure control valve, the membrane 320 makes a stroke movementin the direction of the valve dome or valve seat 52, thereby reducingthe cross-sectional area of the flow channel 340. This increases theflow resistance of the pressure control valve over the valve seat 52.

The control behavior of the pressure control valve can be adjusted viathe diameter cross-section ratios Ø_(M), Ø_(D) of the membrane 320 andthe inner diameter of the sealing surface 52 or the end surface of theclean fluid discharge element 50 that faces away from the filter element100. FIG. 10 illustrates the cross-section diameter Ø_(M) of themembrane 320 (which, in the present embodiment, is defined by the rollpoint of the membrane 320) and the cross-section inner diameter Ø_(M) ofthe sealing surface 52.

The valve closing body 310 is in the rest position (closed position)when

-   -   a) the force F of the return spring 330    -   b) minus the differential pressure Δp from the atmospheric        pressure and the crankcase pressure 610, multiplied by the        cross-sectional area A_(D) (defined by the inner diameter Ø_(D)        of the valve seat 52)    -   c) minus the differential pressure Δp from the atmospheric        pressure and the suction pressure 600, multiplied by the        cross-sectional area A_(M) (defined by the ring between the        cross-section diameter Ø_(M) of the membrane 320 and the inner        diameter Ø_(D) of the valve seat 52) equals zero.        In summary, this gives:        0=F _(return spring 330)        −F(_((crankcase pressure 610))−F(_(suction pressure 600))=F        _(return spring 330)        −Δp(_(atmospheric pressure−crankcase pressure))*A _(D)        −Δp(_(atmospheric pressure−suction pressure))*A _(M)

The return spring 330 prevents the membrane 320 from being permanentlyclosed at small suction vacuum pressures 600 from the turbocharger orintake duct of the engine. In addition, the location of the pressurecontrol characteristics can be varied by means of the return spring 330.This means that with a harder return spring 330, the suction vacuumpressure 600 can act more intensely on the crankcase, and the curveshifts downward.

FIG. 11 illustrates an exemplary control characteristic line of apressure control valve. The Y-axis represents the pressure prevailing inthe inlet for pre-filtration fluid 222 or on the pre-filtration side250—in particular, the crankcase pressure—in hectopascals [hPa]. TheX-axis represents the pressure prevailing in the clean air outlet 212—inparticular, the suction vacuum pressure—in hectopascals [hPa]. The firstcontrol characteristic line, represented in FIG. 11 with a solid line,shows the pressure ratios at a volume flow in the pressure control valveof 100 liters per minute. The second control characteristic line,represented in FIG. 11 with a dashed line, shows pressure ratios at avolume flow in the pressure control valve of 20 liters per minute. Thecontrol range of the two control characteristic lines—shown by way ofexample—lies in the range of −2 to −28 hPa. The slope of the ranges ofthe two control characteristic lines marked with the reference signs700, 702 depends on the area ratios A_(D) and A_(M) of the valve seat 52and the membrane 320. The intersection of the two control characteristiclines with the Y-axis, marked with the reference signs 710, 712, showsthe pressure drop with the pressure control valve is open.

As depicted in FIG. 11, the pressure drop of the oil separator 200 alsoaffects the situation of the pressure control curve, wherein when thepressure drop or volume flow increases, the situation of the pressurecontrol curve rises. Conversely, the crankcase pressure decreases with alower volume flow.

The ratio of the cross-section diameters Ø_(M) and Ø_(D) of the membrane320 and the sealing surface 52 influences the slope 700, 702 of thepressure control curve. If a negative pressure prevails in the crankcaserelative to the atmosphere, and the pretension of the return spring 330is overcome, then the membrane 320 moves onto the sealing surface 52,and the flow resistance increases.

First, if the suction vacuum pressure 600 is large enough and the returnspring 330 is compressed, this results in a curved curve, and finally ina minimum of the crankcase pressure.

At even higher suction vacuum pressures, a slight increase in thepressure 610 is to be observed in the interior 12 of the filter medium,in particular, the crankcase pressure. In these operational ranges, themembrane 320 closes the suction side of the valve intermittently, andthus throttles or interrupts the volume flow. This intermediate pressureis higher than the minimum pressure, because when the valve seat 52 isclosed and there is a strong suction vacuum pressure 600, the pressure610 in the crankcase must be correspondingly higher, in order to for themembrane 320 to again be lifted off from the valve seat 52 against thesuction vacuum pressure acting on the outside thereof.

The oil separator 200 may have an overpressure valve 800 (FIG. 1), forsafety reasons. This overpressure valve may be configured, for example,as is described in DE 10 2013 005 624 A1.

FIG. 8 illustrates the components of an embodiment of a filter element100 according to the present invention. This filter element 100 isconfigured for the crankcase ventilation system illustrated in FIG. 1.The filter element 100 has a cover element, in particular, an end plate40. This end plate 40 covers the covering surface 30 (see FIG. 3) of thefilter medium 10 facing the clean fluid outlet 212, and is connectedsealingly thereto, so that the fluid flows through the filter medium 10into the interior 12 of the filter medium 10. The filter element 100 isan annular coalescence element. For this purpose, the filter element 100has, as preferred, a filter medium 10 configured as a non-woven fabricthat is wrapped repeatedly and thus in a plurality of layers annularlyaround the central tube 70 (also called a support tube). The centraltube 70 allows for flow therethrough and therefore has openings. Thiscan be realized, for example, by a lattice-shaped configuration—as shownin FIG. 8—by means of a perforated plate or the like. The filter medium10 is a non-woven wrap. For stabilization and sealing, it is preferablysealingly connected at each of the end faces—for example, by means ofgluing or welding—to cover elements 40, 42 configured as end plates. Theconstruction of the coalescence element with the wrapped non-wovenfabric is thus fundamentally different from other filter elements, whichare intended to separate solid particles from fluids such as air or oiland generally have a pleated filter medium.

The sealing surface 52 on the clean fluid discharge element 50 is spacedapart from the axial outer surface of the cover element 40. The axialinstallation space required for the clean fluid outlet 212 is therebybridged. The length of the clean fluid discharge element 50, as measuredfrom the axial, outer surface of the cover element 40, corresponds tothe diameter of the clean fluid outlet 212 of the upper housing part210. This makes it possible to achieve a streamlined overall design withwhich the positioning of the sealing surface 52 on the cover element 40or on the filter element 100 is not accompanied by disadvantages.

The cover element 40 is configured as an end plate of the filter element100, as is preferred, in the embodiment illustrated in detail in FIGS.2, 3, and 8. The cover element is sealingly and non-releasably connectedto the filter medium at an end face of the filter element, for example,by gluing or welding. The cover element 40 is preferably produced fromthermoplastic polymer, preferably by injection molding.

The clean fluid discharge element 50 is integrally, sealinglyconnected—as is preferred—to the cover element 40 in the embodimentillustrated in detail in FIGS. 2, 3, and 8.

The clean fluid discharge element 50 is preferably acircular-cylindrical, straight tube, as also illustrated in thedrawings. This tube comprises a closed cylindrical wall and two openends, wherein the sealing surface 52 is configured on one end that facesaway from the cover element, and the other end is connected to the coverelement 40, so that a fluid connection to the interior 12 of the filtermedium 10 or filter body is formed. The ends are preferably oriented soas to be perpendicular to the central axis.

In the embodiment illustrated in detail in FIGS. 2, 3, and 8, as ispreferred, the cover element 40 is configured as an annular end plateaway from which the clean fluid discharge element 50, configured as atube, extends integrally on the side facing away from the filter medium10. The clean fluid element and the cover element preferably form asubstantially L-shaped or alternatively T-shaped cross-section, as isillustrated.

The crankcase ventilation system has two spaces that must be separatedfrom one another—namely, the pre-filtration space or pre-filtration side250, on which the not-yet-cleaned blow-by gas is located, and thepost-filtration space or post-filtration side 240, on which the cleanedgas is located. In addition, the pre-filtration space 250 andpost-filtration space 240 must also be separated from the atmosphere. Tosolve this problem only with a seal, the filter element 100—illustrated,for example, in FIG. 8—has a sealing element configured as a combinationseal, namely, a filter element seal 60 that makes it possible toseparate all three regions from one another.

The filter element seal 60 (see FIGS. 2, 3, and 8) thus serves to sealoff

-   -   the pre-filtration side 250 of the filter element 100 from the        post-filtration side 240 of the filter element 100,    -   the interior of the housing upper part 210 to the ambient air        pressure, and    -   the interior of the housing lower part 220 to the ambient air        pressure.

A special advantage of the filter element seal 60 illustrated in FIGS.2, 3, and 8 over filter element seals from the prior art is thefunctional decoupling of two sealing functions, namely, the sealing offof the interior of the filter housing 210, 220 from the environment onone hand, and the sealing off of the pre-filtration side 250 from thepost-filtration side 240 on the other hand. The two sealing regionsillustrated in FIGS. 2 and 8—namely, the radially sealing region 64 andthe axially sealing region 66—are functionally independent, butintegrated into one part, namely, the sealing element 60.

The filter element seal 60 illustrated in FIGS. 2, 3, and 8 thus has aregion 64 that is radially compressed by means of a defined force, and aregion 66 that is axially compressed by means of a defined force,wherein the radially compressed region 64 and the axial compressedregion 66 are connected to one another and form a continuous sealingelement, which fulfills two independent sealing functions. The sealingforces are defined by a person skilled in the art, by designing thesealing parameters of Young's modulus, seal dimensions, and sealing gapdimensions.

A defined radial seal can be provided in the oil separator 200illustrated in FIGS. 2, 3, and 8 by radially compressing the filterelement seal 60 by means of a defined force between the housing upperpart 210 and the end plate 40. This is advantageously achieved by theextension of the housing upper art 210 to the height of the end plate40, the end plate 40 thus being arranged over the housing edge of thehousing upper part 210.

The radially sealing region 64 may be configured in the manner of anO-ring (see FIGS. 2 and 3). The axially sealing region 66 is, inparticular, configured in the form of a bead having a substantiallyrectangular cross-section, and preferably also has two opposite sealingsurfaces that are in sealing contact with the housing upper part 210 andlower housing part 220, and are compressed axially between the housingparts. In this case, the filter element seal 60 is composed of an O-ringand an axial seal, which are produced in combination.

In the interior 12 of the filter medium 10, a central tube 70 configuredas a support element for the filter medium 10 may be arranged. Thecentral tube supports the filter medium 10 and protects same againstcollapse.

In order to ensure that the fluid flows through the filter medium 10into the interior 12 of the filter medium 10, the filter element 100 hasanother cover element 42—in particular, another end plate 42—on the endthereof that faces the oil outlet 230.

In order to seal off the post-filtration side of the filter element fromthe pre-filtration side of the filter element, another filter elementseal 62—configured, for example, as an O-ring—may be associated with theadditional cover element 42, in order to seal off the additional coverelement 42 from the housing part 220. This additional filter elementseal 62 is preferably arranged radially outward on the additional coverelement 42. The cover element 42 is also preferably configured as an endplate, in particular, as an open end plate having a central opening forthe oil drain.

FIG. 9 illustrates an exploded view of the components of pressurecontrol arranged in the upper housing part 210. The sealing surface 52is also a component of pressure control. Because the sealing surface 52is arranged on the filter element 100, the sealing surface is depictedin FIG. 8.

The valve closing body 310 and the membrane 320 perform a verticalstroke movement in the pressure control (see FIG. 9). In this verticalstroke movement, the valve closing body 310 and the membrane 320 aremoved to the filter element 100 and away from the filter element.

The components of pressure control illustrated in FIG. 9 include:

-   -   the pressure control element cover element 214, which is        configured to cover the first housing part 210 and has an        opening to the atmosphere;    -   the valve closing body 310;    -   the membrane 320;    -   preferably at least one insert 350 that is arranged between the        membrane 320 and the valve closing body 310 and is configured        for pressure control;    -   the return spring 330; and    -   the first housing part 210.

The return spring 330 is arranged on the side of the valve closing body310 that faces away from the valve seat 52, and is supported down in theinsert 350, which preferably also has an opening. The return spring 330is thus located on the atmosphere side. The valve closing body 310preferably has at least one and particularly preferable—as is presentlyshown—three or four continuations 311 that protrude through at least oneopening of the insert 350. The return spring may thus preferably beaxially mounted between the insert 350 and the continuation orcontinuations 311, in particular, the hooks at the end of thecontinuations. In this manner, the return spring 330 can exert anopening force—in particular, a force oriented away from the sealingsurface 52—on the valve closing body.

FIGS. 12 and 13 illustrate an embodiment of an oil separator 200′ of acrankcase ventilation system according to the prior art. The pressurecontrol of this oil separator 200′ is located on the side of the secondhousing part 220′. The valve closing body 310′ has the form of a dish.The valve seat 52′ is here injection-molded onto the housing outside.The seal between the valve seat 52′ and the valve closing body 310′happens hard to hard, in particular, through identical materials of thetwo components. This combination of identical materials of the valveseat 52′ and the region of the valve closing body 310′ that can bebrought into contact with the valve seat 52′ negatively affects thesealing behavior.

According to an advantageous embodiment, it is provided that the returnspring 330 is located on the atmosphere side in the embodiment of thepresent invention illustrated in FIG. 1 to 11. Preferably, the returnspring is protected in a space formed by the membrane 320 and the valveclosing body 310 on one side and by the pressure control valve coverelement 214 on the other side. Arrangement on the outside of the fluidflow protects the spring against the influence of impurities that arecontained in the fluid flow and are deposited on the spring.

In contrast to the filter medium 100 illustrated in FIGS. 2 and 3, thefluid flows through the filter medium according to the prior art that isillustrated in FIG. 12 from inside to the outside. The direction of flowof the fluid is marked with an arrow.

Instead of a combination seal, the crankcase ventilation systemillustrated in FIG. 12 has two separated O-rings 60″ in order to sealthe post-filtration side 240 of the filter element 100 off from theenvironment and seal the pre-filtration side 250 of the filter element100 off from the post-filtration side 240 of the filter element 100.

LIST OF REFERENCE SIGNS

-   10 Filter medium, in particular, non-woven wrap-   12 interior or cavity enclosed by the filter medium 10-   20 direction of flow of the fluid to be filtered; in particular,    direction of flow of the pre-filtration fluid 500 flowing through    the filter medium 10, in the present invention (see FIGS. 2 and 3)-   30 Covering surface of the filter medium 10-   32 Outer surface of the filter medium 10-   40 Cover element of the filter medium 10; in particular, end plate    of the filter medium 10 that faces the clean fluid outlet 212-   42 Additional cover element of the filter medium 10; in particular,    end plate of the filter element 100 that faces the oil outlet 230-   44 Fastening contour of the end plate 40 configured in order to    fasten the sealing element 60-   46 Support contour of the end plate 40 (see FIG. 8)-   50 Clean fluid discharge element; in particular, dome or nozzle    configured in order to remove the clean fluid—for example, a tubular    clean fluid discharge element-   52 Sealing surface, in particular, valve seat of the filter element    100 of the present invention-   52′ Valve seat in the prior art (FIGS. 12 and 13)-   60 Sealing element according to the present invention (see FIGS. 2,    3, and 8); in particular, a filter element seal, for example, to    seal the pre-filtration side of the filter element 100 off from the    post-filtration side of the filter element 100, and to seal the    interior of the filter housing off from the environment;-   60″ Second embodiment for a sealing element, in particular, for a    filter element seal according to the prior art (see FIG. 12)-   62 Additional filter element seal; in particular, O-ring-   64 Radially sealing region of the sealing element 60; in particular,    a compressed region of the sealing element 60 within the filter    housing-   66 Axially sealing region of the sealing element 60; in particular,    a compressed region of the sealing element 60 between the first    housing part 210 and the additional housing part 220-   70 Support element, in particular, central tube, of the filter    element 100-   100 Filter element; in particular, annular filter element, for    example, replaceable filter element or exchangeable element-   110 Longitudinal axis of the annular filter element 100 or the    housing body 220 (see FIG. 8)-   120 Radius of the annular filter element 100 or the housing body 220    (see FIG. 8)-   130 Axis of rotation (see FIG. 2)-   200 Oil separator of the crankcase ventilation system of the present    invention (FIG. 1 to 4, 9, and 10)-   200′ Oil separator of the prior art (FIGS. 12 and 13)-   210 First or upper housing part of the oil separator 200; in    particular, housing cover of the filter housing of the oil separator    200-   212 Clean fluid outlet of the oil separator 200 of the present    invention; in particular, clean fluid outlet of the first or upper    housing part 210-   212′ Clean fluid outlet of the oil separator of the prior art (FIGS.    12 and 13)-   214 Pressure control valve cover element-   220 Additional, second, or lower housing part of the oil separator    200 of the present invention (FIGS. 1 to 3 and 10); in particular,    housing body of the filter housing of the oil separator 200-   220′ Lower housing part of the oil separator 200′ of the prior art    (FIGS. 12 and 13)-   222 Inlet for pre-filtration fluid, in particular, for    oil-containing gas, for example, for oil-containing air, of the oil    separator 200 of the present invention (FIGS. 1, 2, and 4)-   222′ Inlet for pre-filtration fluid, in particular, for    oil-containing gas, for example, for oil-containing air, of the oil    separator of the prior art (FIGS. 12 and 13)-   230 Oil outlet-   240 Post-filtration space or post-filtration side of the filter    element 100 of the present invention-   240′ Post-filtration space or post-filtration side of the filter    element according to the prior art (see FIG. 12)-   250 Pre-filtration space or pre-filtration side of the filter    element 100 of the present invention-   250′ Pre-filtration space or pre-filtration side of the filter    element according to the prior art (see FIG. 12)-   310 Valve closing body, in particular, control pin, of the oil    separator 200 of the present invention-   310′ Valve closing body, in particular, control pin, of the prior    art (FIGS. 12 and 13)-   311 Continuations; in particular, hook-shaped continuations which    protrude upward from the valve closing body and with which the    return spring 330 can engage, the continuations preferably being    integral with the valve closing body-   312 Contact surface of the valve closing body for contacting with    the sealing surface 52 of the filter element 100, in particular, in    order to close the valve-   320 Valve closing body sealing element; in particular, a membrane    surrounding the valve closing body 320, for example, a membrane    extending between the valve closing body 310 and the first housing    part 210-   320′ Valve closing body sealing element of the prior art (FIGS. 12    and 13)-   330 Return spring of the oil separator 200 of the present invention-   330′ Return spring of the prior art (FIGS. 12 and 13)-   340 Flow channel arranged between the valve closing body 310, in    particular, the valve closing body sealing element 320, and the    sealing surface 52-   350 Insert configured for pressure control-   410 Housing of the crankcase ventilation system-   500 Pre-filtration fluid, in particular, oil-containing gas, for    example, oil-containing air-   510 Clean fluid, in particular, clean gas, for example, clean air-   600 Force exerted through the pressure prevailing in the clean air    outlet 212, in particular, suction pressure, for example, suction    vacuum pressure-   610 Force exerted through the pressure prevailing in the interior 12    of the filter medium 10, in particular, the crankcase pressure-   620 Force exerted through the return spring 330-   700 Range of the first control characteristic line where the slope    thereof is dependent on the dimensions, in particular, on the area    ratios A_(M)/A_(D)-   702 Range of the second control characteristic line where the slope    thereof is dependent on the dimensions, in particular, on the area    ratios A_(M)/A_(D)-   710 Point of intersection of the first control characteristic line    with the Y-axis, which shows the pressure drop when the pressure    control valve is open-   712 Point of intersection of the second control characteristic line    with the Y-axis, which shows the pressure drop when the pressure    control valve is open-   720 Inflection point of the first control characteristic line as a    function of the compression spring or spring rate of the return    spring 330-   722 Inflection point of the second control characteristic line as a    function of the compression spring of the return spring 330 or the    spring rate of the return spring 330-   800 Overpressure valve-   A_(M) Cross-sectional area of the membrane 320-   A_(D) Cross-sectional area of the inner diameter Ø_(D) of the    sealing surface 52, or the cross-sectional area of the inner    diameter of the end surface of the clean fluid discharge element 50    facing away from the filter element 100-   Ø_(M) Cross-section diameter of the membrane 320-   Ø_(D) Cross-sectional inner diameter of the sealing surface 52 or    inner diameter of the end surface of the clean fluid discharge    element 50 facing away from the filter element 100

What is claimed is:
 1. A filter element for an oil separator of acrankcase ventilation system, the filter element comprising: at leastone filter medium surrounding a central axis, the at least one filtermedium configured to separate oil from aerosol, the at least one filtermedium having an axial end surface forming a covering surface extendingin a radial direction relative to the central axis; and a cover elementformed as an annular end plate, fixed onto and fully covering thecovering surface of the at least one filter medium; wherein the coverelement forms a tubular projection on an axially outer surface of thecover element, the tubular projection projecting axially outwardly awayfrom the at least one filter medium, the tubular projection having anopen interior which opens through the cover element into an interior ofthe at least one filter medium, wherein the tubular projection is aclean fluid discharge element configured to remove cleaned fluid from aninterior of the filter element; wherein an axially outer end of thetubular projection of the filter element has an annular sealing surfaceforming a valve seat; wherein the tubular projection is configured as aclean fluid discharge element that extends away from the filter elementand is configured to remove cleaned fluid from an interior of the filterelement to the valve seat of the cover element; wherein the valve seatof the cover element is configured as a sealing surface for a pressurecontrol valve body of the crankcase ventilation system to sealably closeagainst.
 2. The filter element according to claim 1, wherein the filterelement is oval-cylindrical; and wherein the filter element has a cavityin the interior of the at least one filter medium; wherein the fluid tobe filtered flows from the outer surface of the filter medium to thecavity; and wherein the cavity is connected directly to the clean fluiddischarge element in order to remove the cleaned fluid.
 3. The filterelement according to claim 1, wherein the clean fluid discharge elementand/or the annular sealing surface is formed of at least onemechanically fixed and/or rigid material; wherein the at least onemechanically fixed and/or rigid material is a moldable material selectedfrom the set consisting of: polyurethane, polyamide, or polyamide formedfrom polyamide 66 with 35% glass fiber (PA 66 GF 35).
 4. The filterelement according to claim 1, wherein the annular sealing surface, theclean fluid discharge element, and the cover element are integrallyformed as a unitary one-piece component.
 5. The filter element accordingto claim 1, wherein the at least one filter medium is a multi-layerednon-woven wrap.
 6. The filter element according to claim 1, wherein thecover element and clean fluid discharge element are continuously closed.7. An oil separator for a crankcase ventilation system, comprising: anoil separator housing including: a first housing part; and a secondhousing part secured to the first housing part and enclosing a chambertherein; a filter element according to claim 1 arranged in the chamberof the oil separator housing; wherein the first housing part includes atleast one oil separator clean fluid outlet configured to remove thecleaned fluid the pressure control valve is configured to limit thenegative pressure applied in the crankcase ventilation system, thepressure control valve formed in combination by: the valve seat of thefilter element; and a valve closing body accommodated in the firsthousing part that operates in conjunction with and sealably closesagainst the valve seat; wherein the sealing surface of the tubularprojection of the cover element of the filter element forms the valveseat against which the valve closing body sealably closes when thepressure control valve is in a closed state.
 8. The oil separatoraccording to claim 7, wherein the valve closing body comprises at leastone elastic valve closing body sealing element, at least on a regionthereof arranged to contact with the valve seat of the filter element;and wherein the at least on a region of the at least one valve closingbody is surrounded by an elastic valve closing body sealing element onthe region thereof that is arranged to contact with the valve seat ofthe filter element.
 9. The oil separator according to claim 8, whereinthe valve closing body sealing element is formed out of at least oneelastomer; wherein the at least one elastomer are selected from the set:ethylene acrylate rubber (EAR) and/or from acrylate rubber and/or fromhydrogenated nitrile rubber (H)NBR.
 10. The oil separator according toclaim 7, wherein the valve closing body sealing element is connectedfixedly, non-releaseably to the valve closing body; wherein the valveclosing body sealing element is applied onto the valve closing body by aspray process.
 11. The oil separator according to claim 7, wherein thevalve closing body is flat or level on the region thereof that faces thevalve seat and contacts with the valve seat of the filter element. 12.The filter element according to claim 1, wherein the annular sealingsurface of the tubular projection is circular, substantially flat andfree of burrs.
 13. The filter element according to claim 1, wherein acircumferential edge of the annular sealing surface of the tubularprojection is rounded.
 14. A method for limiting the crankcase vacuum ofa crankcase ventilation system to a predetermined value, comprising:providing an oil separator housing enclosing a chamber therein;providing a filter element configured to separate oil from fluid,including: at least one filter medium surrounding a central axis, the atleast one filter medium configured to separate oil from aerosol, the atleast one filter medium having an axial end surface forming a coveringsurface extending in a radial direction relative to the central axis;and a cover element formed as an annular end plate, fixed onto and fullycovering the covering surface of the at least one filter medium; whereinthe cover element forms a tubular projection on an axially outer surfaceof the cover element, the tubular projection projecting axiallyoutwardly away from the at least one filter medium, the tubularprojection having an open interior which opens through the cover elementinto an interior of the at least one filter medium, wherein the tubularprojection is a clean fluid discharge element configured to removecleaned fluid from an interior of the filter element; wherein an axiallyouter end of the tubular projection of the filter element has an annularsealing surface forming a valve seat; wherein the tubular projection isconfigured as a clean fluid discharge element that extends away from thefilter element and is configured to remove cleaned fluid from aninterior of the filter element to the valve seat of the cover element;wherein the valve seat of the cover element is configured as a sealingsurface for a pressure control valve closing body of the crankcaseventilation system to sealably close against; and providing the pressurecontrol valve configured to limit the negative pressure applied in thecrankcase ventilation system, the pressure control valve formed incombination by: a valve closing body that operates in conjunction withvalve seat of the cover element; wherein the sealing surface of thefilter element forms the valve seat against which the valve body closes;arranging the filter element replaceably in the chamber of the oilseparator housing; arranging the valve closing body of the pressurecontrol valve in the oil separator housing such that the valve closingbody is closeable against the valve seat of the filter element;operating the pressure control valve responsive to prevailing pressurein the crankcase ventilation system to limit the crankcase vacuum suchthat the valve closing body is moved relative to the filter element andthe valve seat of the filter element to control crankcase vacuum.